Cold rolling mill and a rolling method

ABSTRACT

The present invention controls the ever-changing thermal crowns to give good strip shapes during rolling without causing any flaws in the rolled surfaces and with quick responses to ever-changing thermal crowns. A 6-high rolling mill in accordance with the present invention wherein each of the working rolls  2  which are equipped with a shifting means has a locally gradually-thickened-toward-end part (or a local concave crown  2   a ) on one end of the roll, the working rolls  2  are disposed so that the locally gradually-thickened-toward-end parts of the working rolls  2  may be vertically symmetrically with a point, a decremental bender  10   b  which works to narrow the gap between the working rolls is provided as a first shape control means, both the local concave crowns  2   a  and the roll bender  10   b  are used to control thermal crowns, and an incremental bender  11   a  which controls bending of the intermediate rolls  3  is provided as a second shape control means which controls so that the center of a strip may have a concave crown.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a cold rolling mill and arolling method, more particularly, to a cold rolling mill of four-highor more-high for a reversible cold rolling facility, aluminum rollingfacility, or copper rolling facility and a rolling method using saidcold rolling mill.

[0003] 2. Description of Prior Art

[0004] In rolling of a steel strip, roll diameters will vary along thewidths of the rolls due to thermal changes in the axial direction ofeach working roll and the resulting differences of roll expansions. Thisphenomenon is called a thermal crown. In other words, this is becausethe roll parts which the hot strip touches are heated much hotter thanthe other roll parts by heats caused by rolling and heats caused byfrictions between the roll surfaces and the rolled strip. When thisthermal crown is big, strip edges will be thicker than any other stripparts, which is called “Edge up.” This makes the rolled strip haveuneven thickness and reduces the yield of the rolling products.Similarly, when this thermal crown is big, the rolling tension will begreater on the strip edges or the vicinity and the strip edges arepulled too much (due to uneven tension distribution of the strip). Thisextremely increases the possibility of breaking the strip. Particularly,when the rolled metal is soft such as aluminum or copper, its quantityof an edge drop which is a sharp reduction of the strip thickness due tothe Hertz flattening of the roll near the edges is smaller than that ofgeneral steel strips. Consequently, the thermal crown effect appearsrelatively greater and the rolling becomes more dangerous. Particularlyin aluminum rolling which generally uses combustible rolling oil of alow flashing point, sparks due to a sheet may break ignite the rollingoil and may cause a fire. In such a state, to prevent the aboveproblems, the rolling must be carried out carefully with the rollingspeed reduced. This not only reduces the operability but also theproductivity.

[0005] Similarly, the edge-up phenomenon caused by a thermal crown isalso harmful to a reversible cold rolling facility which repeatedlyrolls a steel strip which is supplied from and taken up by a singlereel. When the reel takes up a rolled strip having its edges increased,the taken-up strip on the reel has a spool-like shape (or a built-upshape) which may easily cause skewing and loosing of the strip andconsequently cause the strip surfaces to be damaged. Particularly, inthe cold reversible rolling equipment, it is very hard to completelyremove the rolling oil from the surface of the rolled strip. Thisrolling oil makes the strip on a reel slippery and uncoiled easily.Naturally, this is a great enemy to the operability and quality ofrolling products.

[0006] To solve problems to be caused by thermal crowns in cold rolling,coolant controlling has been employed conventionally. Below will beexplained technologies related to thermal crown controlling in both coldrolling and hot rolling together with a conventional technology relatedto the locally gradually-thickened-toward-end part formed on one end ofeach working roll in accordance with the present invention.

[0007] <Coolant Control>

[0008] For example, as disclosed by “Effect of Coolant Zone Control inShape Control During Cold Aluminum Rolling” (“Plasticity and Working”Vol.23, No.263 (December, 1982)), this technology controls the rate ofcooling the rolls perpendicularly to the movement of the strip to removethe problem caused by a thermal crown. This is called “Coolantcontrolling.” Another coolant control applies hotter coolant to thestrip edges. However, these conventional coolant control technologiesare not effective enough to solve problems caused by thermal crowns.Particularly, as the aluminum or copper rolling facility uses mineralcoolant (oil) which is more viscous than water-soluble coolant used by asteel rolling facility, the coolant cooling is less effective to controlthermal crowns in the aluminum or copper rolling facility.

[0009] <Hot Rolling—Initial Concave Crown on the Full Length of theWorking Roll>

[0010] Such thermal crown related problems occur also in hot rolling.However, the hot rolling facility handles thicker strip (1.6 mm thickminimum) than the cold rolling facility (0.2 mm thick or under) andrelatively has less influence by thermal crowns. Further, the hotrolling oil or cooling water applied to the surface of a strip to berolled is burnt or evaporated almost completely before the rolled stripis taken up and will hardly remain on the surface of the rolled strip.Even if a slight oil will never cause slippage in strata of the coilbecause the strip strata of a hot-rolled material have greater frictions(e.g. due to scales on the surface of the material) than those of acold-rolled material. Further the quality control of hot rolledmaterials is not severer than that of cold-rolled materials as they arefrequently used as construction materials. Therefore, thermal crowncontrolling of the hot rolling need not be so strict. To solve thethermal-crown problems and to prevent roll abrasion, the rollingfacility employs, for example, working rolls each of which isclub-shaped from the center to each end of the roll to form a concavecrown on the roll. Contrarily, as the cold rolling products are requiredto have high quality, it is very important to strictly control thermalcrowns.

[0011] <Japanese Non-examined Patent Publication No.9-239411 (1997)>

[0012] In case a hot rolling facility uses high-speed-steel workingrolls having excellent abrasion resistance, thermal crown controlling isvery significant for the hot rolling facility because thehigh-speed-steel working rolls have great coefficients of linearexpansion. For effective thermal crown controlling, this patentpublication discloses a 4-high rolling mill having shiftable workingrolls each of which increases its diameter from the center to one end ofthe roll (to form a half concave crown). This technology is veryeffective for thermal crown controlling. However, this technology is notgood for cold rolling. When it is applied to cold rolling, the rolledstrip is deformed and has flaws on the surface (to be explained later).

[0013] <Japanese Non-examined Patent Publication No.5-76905 (1993)>

[0014] This patent publication discloses a cold tandem rollingtechnology which increases the diameter of one end of each of workingrolls (to give a locally concave crown) for other than thermal crowncontrolling. This technology is to prevent cracking in the strip edges(so-called edge cracking) which may occur in cold rolling of brittlesilicon steel. This technology uses working rolls each of which has agradually-thickened-toward-end part (increasing the diameter) on its endto form a local concave crown there in the first roll and working rollseach of which has a tapered part on its end to form a local convex crownthere in the second roll and later. In other words, the working rolls inthe first roll strongly presses the edges of the stripe by the localconcave crowns of the working rolls to generate residual rollingstresses there and prevent the edge cracking (which may occur in coldrolling of brittle silicon steel). This strong pressing in the firstroll increases the edge drop. To compensate, the second and later rollsuse working rolls having locally convex crowns.

[0015] <Japanese Non-examined Patent Publication No.11-123431 (1999)>

[0016] This patent publication discloses a cold tandem rollingtechnology which increases the diameter of one end of each of workingrolls (to give a locally concave crown) for other than thermal crowncontrolling. The object of this technology is to prevent generation ofheat scratching and strip break in cold tandem rolling. This technologyuses a pair of upper and lower working rolls each of which increases thediameter towards one end of the roll. Said pair of upper and lowerworking rolls are disposed symmetrically with a point and made to shiftaxially to load a bending force. With this, the technology cold-rolls astrip at a tension-load ratio of 0.3 or above. The shift of the workingrolls is controlled to get a desired elongation at the strip edges andthe bending force of the working rolls is controlled so that the stripmay have a flat center. This technology enables stable rolling without astrip break and a heat scratches at a higher rolling speed.

SUMMARY OF THE INVENTION

[0017] As explained above, thermal crowns cause various problems in coldrolling. To solve such problems, a coolant control technology whichcontrols the rate of cooling the rolls across the movement of the striphas been employed, but is not sufficient to solve the problems. Further,the thermal crown changes every moment even while an identical materialis rolled and the coolant control is not quick enough to answer to suchever-changing thermal crown.

[0018] Conventionally, the ever-changing thermal crown has beencontrolled by a technology which gives an initial concave crown to thefull length of the working rolls in hot rolling or by a technology whichuses shiftable working rolls each of which increases the diameter fromthe center of the roll to one end of the roll to give a concave crown(half crown) as disclosed in Japanese Non-examined Patent PublicationNo.9-239411 (1997). These technologies change the position of theworking rolls according to the change of the thermal crown to controlthem. However, moving the working rolls while rolling is in progressmust be avoided because it may give flaws to the rolled surfaces.Particularly, it must be avoided in cold rolling, more particularly incold rolling of soft materials such as aluminum. Further thesetechnologies are slow in answering to the ever-changing thermal crowns.

[0019] The technologies disclosed in Japanese Non-examined PatentPublications No.5-76905 (1993) and No.11-123431 (1999) use the workingrolls each of which has an end portion thickened-toward-end (to have alocal concave crown) for other than thermal crown controlling. Even ifthe shiftable working rolls having local concave crown are used to solveproblems related to thermal crowns, problems pertaining to surface flawsand slow responsibility are left to be solved.

[0020] To control the ever-changing thermal crowns during rolling, it isassumed to be also possible to use the working rolls having a half crownor local concave crown together with a so-called roll bending technologywhich applies external forces to the ends of the working rolls to bendthe working rolls. In this case, problems pertaining to surface flawsand slow responsibility can be solved by controlling the working rollbender according to the change of the thermal crown during rollinginstead of moving the working rolls.

[0021] The difficulty in controlling the thermal crown is due to localroll deformation near strip edges by thermal expansion of the rolls. Ingeneral, it is very hard or the roll bending technology to controlthermal crowns generated by such a local thermal roll deformation nearstrip edges. This is because the roll bending technology bends theworking rolls over the full length of the rolls and cannot control thelocal deformation of the rolls near the strip edges.

[0022] When the ever-changing thermal crown is controlled only by theworking roll bender during rolling, the crown on in the center of therolled strip (hereinafter sometimes called a body crown) also variesgreatly. Therefore, even when the working rolls are initially positionedproperly, the thermal crown near the strip edges increases as rollingprogresses. In this case, when the roll bender is used to control thethermal crown, the body crown changes and the strip shape becomes worse.This is because the shape of the thermal crown near strip edges does notmatch the shape of a crown (called an edge crown) formed by the workingroll bender near the strip edges.

[0023] An object of the present invention is to provide a cold rollingmill and a rolling method which rolls strips of an even thickness in thecold state, controlling the ever-changing thermal crowns during rollingwithout causing any flaws in the rolled surfaces and with quickresponses to ever-changing thermal crowns (1) To attain the aboveobject, a cold rolling mill of 4-high or more-high in accordance withthe present invention comprising first shifting equipment which canshift a pair of upper and lower working rolls in opposite directions androll bending equipment which controls the bending of said pair ofworking rolls, wherein said cold rolling mill further comprises

[0024] locally gradually-thickened-toward-end parts provided on theworking rolls at their one ends so as to be vertically symmetrical withrespect to a point,

[0025] a first shape control means for controlling a thermal crownformed on each of said pair of working rolls together with said locallygradually-thickened-toward-end parts, and

[0026] a second shape control means for controlling to form a concavecrown in the center of said rolled material.

[0027] Said locally gradually-thickened-toward-end parts, said firstshape control means, and said second shape control means work asfollows. Said first shape control means controls the change of a thermalcrown while a rolling is in progress and said second shape control meanscontrols the whole shape of the rolled material which is controlled bysaid first shape control means (or the change of the body crown).Consequently, these means can carry out cold rolling of strips of aneven thickness, controlling the ever-changing thermal crowns duringrolling without causing any flaws in the rolled surfaces and with quickresponses to ever-changing thermal crowns

[0028] (2) In the above description (1), said roll bending equipment ispreferably equipped with a decremental bending equipment which narrowsthe gap between said pair of upper and lower working rolls, and saidfirst shape control means is said decremental bending equipment.

[0029] With this, said first shape control means can control thermalcrowns during rolling without causing problems pertaining to surfaceflaws and responsibility to thermal crowns.

[0030] (3) In the above description (1), said roll mill is a 6-highrolling mill comprising one pair of upper and lower intermediate rollsand a second shifting equipment which can move these intermediate rollsin different directions. Said first shape control means can be saidsecond shape control means.

[0031] With this, said first shape control means can control thermalcrowns during rolling without causing problems pertaining to surfaceflaws and responsibility to thermal crowns.

[0032] (4) To attain the above object, a cold rolling mill of 4-highs ormore in accordance with the present invention comprising first shiftingequipment which can shift a pair of upper and lower working rolls inopposite directions and roll bending equipment which controls thebending of said pair of working rolls, wherein

[0033] each of said upper and lower working rolls has a locallygradually-thickened-toward-end part which increases in diameter towardone end of the working roll,

[0034] said locally gradually-thickened-toward-end parts are disposedvertically symmetrical with respect to a point,

[0035] said roll bending equipment as the first shape control meanscomprises decremental bending equipment which works to narrow the gapbetween said pair of upper and lower working rolls, and

[0036] said rolling mill further comprises a second shape control meansfor controlling to form a concave crown in the center of said rolledmaterial.

[0037] Said locally gradually-thickened-toward-end parts, said firstshape control means and said second shape control means work as follows.Said first shape control means controls the change of a thermal crownwhile a rolling is in progress and said second shape control meanscontrols the whole shape of the rolled material which is controlled bysaid first shape control means, that is, the change of the body crown.Consequently, these means can carry out cold rolling of strips of aneven thickness, controlling the ever-changing thermal crowns duringrolling without causing any flaws in the rolled surfaces and with quickresponses to ever-changing thermal crowns

[0038] (4) To attain the above object, a cold rolling mill of 4-high ormore-high for a cold reversible rolling facility in accordance with thepresent invention comprising first shifting equipment which can shift apair of upper and lower working rolls in opposite directions and rollbending equipment which controls the bending of said pair of workingrolls, wherein

[0039] each of said upper and lower working rolls has a locallygradually-thickened-toward-end part which increases in diameter towardone end of the working roll,

[0040] said locally gradually-thickened-toward-end parts are disposedvertically symmetrically with respect to a point,

[0041] said roll bending equipment as the first shape control meanscomprises decremental bending equipment which works to narrow the gapbetween said pair of upper and lower working rolls, and

[0042] said rolling mill further comprises a second shape control meansfor controlling to form a concave crown in the center of said rolledmaterial.

[0043] Even when this invention is applied to a cold reversible rollingfacility, said locally gradually-thickened-toward-end parts, said firstshape control means and said second shape control means work as follows.Said first shape control means controls the change of a thermal crownwhile a rolling is in progress and said second shape control meanscontrols the whole shape of the rolled material which is controlled bysaid first shape control means, that is, the change of the body crown.Consequently, these means can carry out cold rolling of strips of aneven thickness, controlling the ever-changing thermal crowns duringrolling without causing any flaws in the rolled surfaces and with quickresponses to ever-changing thermal crowns.

[0044] (6) To attain the above object, a cold rolling mill of 4-high ormore-high for a cold aluminum rolling facility in accordance with thepresent invention comprising first shifting equipment which can shift apair of upper and lower working rolls in opposite directions and rollbending equipment which controls the bending of said pair of workingrolls, wherein

[0045] each of said upper and lower working rolls has a locallygradually-thickened-toward-end part which increases in diameter towardone end of the working roll,

[0046] said locally gradually-thickened-toward-end parts are disposedvertically symmetrically with respect to a point,

[0047] said roll bending equipment as the first shape control meanscomprises decremental bending equipment which works to narrow the gapbetween said pair of upper and lower working rolls, and

[0048] said rolling mill further comprises a second shape control meansfor controlling to form a concave crown in the center of said rolledmaterial.

[0049] Even when this invention is applied to a cold aluminum rollingfacility, said locally gradually-thickened-toward-end parts, said firstshape control means and said second shape control means work as follows.Said first shape control means controls the change of a thermal crownwhile a rolling is in progress and said second shape control meanscontrols the whole shape of the rolled material which is controlled bysaid first shape control means, that is, the change of the body crown.Consequently, these means can carry out cold rolling of strips of aneven thickness, controlling the ever-changing thermal crowns duringrolling without causing any flaws in the rolled surfaces and with quickresponses to ever-changing thermal crowns

[0050] (7) In the above descriptions (1) and (4) to (6), said roll millis preferably a 6-high rolling mill comprising one pair of upper andlower intermediate rolls which can move axially. Said second shapecontrol means comprises incremental bending equipment which controlsbending of said upper and lower intermediate rolls.

[0051] With this, said second shape control means can control to form atleast a concave crown in the center of the strip.

[0052] (8) In the above description (7), each of said pair of upper andlower intermediate rolls preferably have a locally tapered part on theside where the gradually-thickened-toward-end part of the working rollexists so that the tapered part may be engaged with said thickened endof each working roll and the rate of diameter changing of said taperedpart is equal to or greater than the rate of diameter changing of thegradually-thickened-toward-end part.

[0053] This locally gradually-thickened-toward-end part suppressescontact pressures of the rolls from increasing and thus makes the rollshave longer service lives.

[0054] (9) In the above descriptions (1) and (4) to (6), said roll millis a 6-high rolling mill having one pair of upper and lower intermediaterolls. Each of said intermediate rolls has a curved roll crowncontaining both a maximum and a minimum all over the roll and saidsecond shape control means can be the shifting equipment which shiftssaid pair of upper and lower intermediate rolls in opposite directions.

[0055] With this, said second shape control means can control to form atleast a concave crown in the center of the strip.

[0056] (10) In the above descriptions (1) and (4) to (6), said roll millis a 6-high rolling mill having one pair of upper and lower intermediaterolls. Said second shape control means can have a roll-crossingmechanism which tilts at least said pair of intermediate rollshorizontally with the center of the mill approximately as the center ofrotation.

[0057] With this, said second shape control means can control to form atleast a concave crown in the center of the strip.

[0058] (11) In the above descriptions (1) and (4) to (6), said roll millis a 4-high rolling mill and said second shape control means can beequipped with a roll-crossing mechanism which tilts said pair of workingrolls or one pair of rolls supporting said working rolls with the centerof the mill approximately as the center of rotation.

[0059] With this, said second shape control means can control to form atleast a concave crown in the center of the strip.

[0060] (12) In the above descriptions (1) and (4) to (6), said roll millis a 4-high rolling mill and each of said pair of rolls for supportingsaid working rolls has a roll crown which is tapered from about thecenter of the roll towards one end of the roll and said roll crowns aredisposed vertically symmetrically with respect to a point. Said secondshape control means can be equipped with the shifting equipment whichcan move said supporting rolls in different directions.

[0061] With this, said second shape control means can control to form atleast a concave crown in the center of the strip.

[0062] (13) In the above descriptions (1) to (12), the diameter of eachof said upper and lower working rolls is preferably expressed by

⅙Wm+50≦Dw≦⅙Wm+250

[0063] wherein

[0064] Dw is the diameter of each of the working rolls and Wm is themaximum width of a sheet to be rolled.

[0065] The decremental bending equipment used as said first shapecontrol means to narrow the gap between said pair of working rolls canassure the effect of controlling the thermal crown.

[0066] (14) To attain the above object, a rolling method in accordancewith the present invention comprises the steps of:

[0067] using shape detectors which measure the shapes of a sheet atleast after being rolled and a 4-high or more-high cold rolling millwhich comprises

[0068] shifting equipment which can shift one pair of upper and lowerworking rolls each of which has a locally gradually-thickened-toward-endpart on one end of respective working rolls with the locallygradually-thickened-toward-end parts disposed vertically symmetricallywith respect to a point,

[0069] roll bending equipment which controls bending of said pair ofworking rolls and has, as a first shape control means, decrementalbending equipment which works to narrow the gap between said pair ofworking rolls, and

[0070] a second shape control means for forming a concave crown in thecenter of said rolled material,

[0071] adjusting the position of said one pair of upper and lowerworking rolls by said shifting equipment so that side edges of therolled sheet may be limited by said gradually-thickened-toward-end partsof said working rolls before starting rolling,

[0072] approximately fixing the shift position of said pair of upper andlower working rolls while rolling is in progress, and

[0073] determining the operations of said first and second shape controlmeans so that their effects on the sheet may work reversely according tothe output of said shape detectors.

[0074] With this, as explained in (1), said first shape control meanscan control the change of a thermal crown while a rolling is in progressand said second shape control means can control the whole shape of therolled material which is controlled by said first shape control means,that is, the change of the body crown. Consequently, these means cancarry out cold rolling of strips of an even thickness, controlling theever-changing thermal crowns during rolling without causing any flaws inthe rolled surfaces and with quick responses to ever-changing thermalcrowns.

[0075] (15) In the above description (14), the operation of said firstshape control means is determined according to the output of said shapedetector placed near the edge of the sheet and the operation of saidsecond shape control means is determined according to the output of saidshape detector placed near the center of the sheet.

[0076] This explicitly classifies the target quantities of operations ofsaid first and second shape control means and makes actual controllingmethods easier and simpler.

[0077] (16) To attain the above object, a rolling method in accordancewith the present invention comprises the steps of:

[0078] using shape detectors which measure the shapes of a sheet atleast after being rolled and a 6-high cold rolling mill which comprises

[0079] first shifting equipment which can shift one pair of upper andlower working rolls each of which has a locallygradually-thickened-toward-end part on one end of respective workingrolls with the locally gradually-thickened-toward-end parts disposedvertically symmetrically with respect to a point,

[0080] second shifting equipment which can shift one pair of upper andlower intermediate rolls which support said working rolls reversely, and

[0081] a second shape control means for forming a concave crown in thecenter of said rolled material,

[0082] adjusting the position of said one pair of upper and lowerworking rolls by said first shifting equipment so that side edges of therolled sheet may be limited by said gradually-thickened-toward-end partsof said working rolls before starting rolling,

[0083] approximately fixing the shift position of said pair of upper andlower working rolls while rolling is in progress, and

[0084] determining the operations of said second shifting equipment andsaid shape control means according to the output of said shapedetectors.

[0085] With this, as explained in (1), said first shape control meanscan control the change of a thermal crown while a rolling is in progressand said second shape control means can control the whole shape of therolled material which is controlled by said first shape control means,or, the change of the body crown. Consequently, these means can carryout cold rolling of strips of an even thickness, controlling theever-changing thermal crowns during rolling without causing any flaws inthe rolled surfaces and with quick responses to ever-changing thermalcrowns.

[0086] (17) In the above description (16), the operation of said secondshifting equipment is determined according to the output of said shapedetector placed near the edge of the sheet and the operation of saidshape control means is determined according to the output of said shapedetector placed near the center of the sheet.

[0087] This explicitly classifies the target quantities of operations ofsaid first and second shape control means and makes actual controllingmethods easier and simpler.

BRIEF DESCRIPTION OF THE DRAWINGS

[0088]FIG. 1 is a vertical sectional front view of a 6-high rolling mill(a cold rolling mill) which is one embodiment of the present invention.

[0089]FIG. 2 is a vertical sectional front view of the embodiment cutalong the lines II to II of FIG. 1.

[0090]FIG. 3 is a vertical sectional front view of the embodiment cutalong the lines III to III of FIG. 1.

[0091]FIG. 4 is a schematic view of the shape R of a thermal crowngenerating on a working roll relative to the center of a strip material1 as the origin.

[0092]FIG. 5 is an explanatory illustration of the dimensions of localcrowns of the working rolls and the intermediate rolls and shifting ofrespective rolls.

[0093]FIG. 6 shows the shapes of thermal crowns used for simulation.

[0094]FIG. 7 shows the result of simulation of rolling by a 6-highrolling mill using straight rolls having no local crowns underconditions of certain thermal crowns.

[0095]FIG. 8 shows the result of the simulation changing the workingroll bending force Fw only.

[0096]FIG. 9 shows the result of the simulation giving local concave andconvex crowns to the end of the working rolls and the intermediaterolls.

[0097]FIG. 10 shows an effect of giving a local convex crown to the endsof intermediate rolls.

[0098]FIG. 11 shows the result of simulation representing therelationship between the shift position setting and the shape controlcharacteristics to explain that controlling together with the rollbenders allows loose setting of working roll positions.

[0099]FIG. 12 shows an explanatory diagram for the ratio of a high-ordercomponent which that the working rolls affect the body crown.

[0100]FIG. 13 shows an example of calculating the change “δCw” of thebody crown, assuming the diameter of the working roll is small.

[0101]FIG. 14 shows preferable ranges of working roll diameters mostsuitable to control thermal crowns using both the local convex crownrolls and roll benders.

[0102]FIG. 15 shows a 6-high rolling mill which is another embodiment ofthe present invention.

[0103]FIG. 16 shows a schematic sectional view of a cross-shift type4-high rolling mill which is one of the embodiments of the presentinvention.

[0104]FIG. 17 shows a schematic sectional view of a 6-high rolling millwhich is still another embodiment of the present invention.

[0105]FIG. 18 shows a schematic sectional view of a 4-high rolling millwhich is a still further embodiment of the present invention.

[0106]FIG. 19 is a schematic illustration of a reversible steel rollingsystem to which an embodiment of the present invention is applied.

[0107]FIG. 20 is a schematic illustration of an aluminum rolling systemto which an embodiment of the present invention is applied.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0108] Some embodiments of the present invention will be explained inmore detail with reference to the accompanying drawings.

[0109]FIG. 1 shows a vertical sectional front view of a 6-high rollingmill (a cold rolling mill) which is one embodiment of the presentinvention.

[0110]FIG. 2 and FIG. 3 respectively show sectional views of theembodiment cut along the lines II to II and III to III of FIG. 1.

[0111] In FIG. 1 to FIG. 3, the 6-high rolling mill comprises workingrolls 2 which directly touch and roll a strip material 1, intermediaterolls 3 in contact with the working rolls, backup rolls 4 in contactwith the intermediate rolls 3, bearing boxes of the backup rolls 4, anda housing 5 which supports the rolls through the bearing boxes. An oiljack 7 on the bottom of the housing 5 lifts up and down the bearingboxes 6 of the backup rolls 4 to change a force to compress the stripmaterial 1. The working rolls 2 and the intermediate rolls 3 arerespectively supported by bearing boxes 8 and 9 at both ends of therolls. Oil-pressure cylinders 10 a, 10 b, 11 a, and 11 b are provided togive forces to said bearing boxes to bend the rolls. Hereinafter, theoil-pressure cylinders 10 a and 11 a which bend the working rolls toenlarge the gap between the working rolls 2 are termed incrementalbending equipment. The oil-pressure cylinders 10 b and 11 b which bendthe working rolls to narrow the gap between the working rolls 2 aretermed decremental bending equipment.

[0112] The working roll 2 and the intermediate roll 3 are equipped withshifting equipment which can shift the rolls 2 and 3 axially. Referringto FIG. 3, an example of the shifting equipment for the working rollwill be explained below. In FIG. 3, the shifting equipment comprises ashift supporting member 12 which supports the bearing box 8 of theworking roll 2 and a shift head 13 which is connected to the shiftsupporting member 12. The shift head 13 is equipped with a shiftcoupling means comprising hooks to easily couple the shift head with thebearing box 8 at one end of the working roll and a coupling cylinder 15.Further, the shift cylinders 16 fixed on the housing 9 are linked to theshift head. With this configuration, the working rolls 2 and the shiftsupporting members 12 can be moved freely by operating the shiftcylinders 16 with the shift coupling means mounted. As the shiftsupporting member 12 contains said bending equipment 10 a, 10 b, 11 a,and 11 b, the working rolls can be shifted without changing the positionof the working point of the bending force. This can increase the shiftstroke.

[0113] The shifting equipment for the intermediate rolls are built up inthe similar manner and is not visible in the accompanying drawings.

[0114] Each of the working rolls 2 of said 6-high rolling mill has alocally gradually-thickened-toward-end part (or a local concave crown 2a) whose diameter increases towards the end of the roll on one end ofthe roll. The working rolls 2 are disposed so that the locallygradually-thickened-toward-end parts of the working rolls 2 may bevertically symmetrically with respect to a point. The upper and lowerworking rolls are rotated in opposite directions by the shift equipmentshown in FIG. 3. The locally concave crowns 2 a work to control thermalcrowns on the working rolls 2. The length of the locally concave crown 2a is preferably equal to or greater than the thermal influence length(to be explained later) of the thermal crown (in general 100 mm to 300mm). Further the concave crown is preferably shaped to cancel thethermal crown of the roll. Generally an approximate quadratic curve isenough. In extreme cases, the concave crown can be a tapered crown foreasy roll cutting although it matches less with the thermal crown.Furthermore, said concave crown can be determined under actual rollingconditions or according to actual rolling results. Usually, the concavecrown is great enough to cancel the maximum thermal crown which occursin actual rolling and the position of the working rolls is adjusted bythe shifting equipment according to the rolling conditions.

[0115] Each of the intermediate roll 3 has a locally tapered part 3 a(or a locally convex crown) on the side where thegradually-thickened-toward-end part of the working roll 2 exists so thatthe tapered part may be engaged with the end thickened-toward-end ofeach working roll 2. This is provided to reduce contact surfacepressures between rolls (that is, between the intermediate roll 3 andthe working roll 2 and between the intermediate roll 3 and the backuproll 4). This can suppress spalling and uneven abrasion of rolls whichare apt to generate on roll ends. This can make the service life of theroll longer.

[0116] To make the description below clearer, characteristics of athermal crown will be explained in detail. FIG. 4 is a schematic view ofthe shape R of a thermal crown generating on a working roll relative tothe center of a strip material 1 as the origin. Referring to FIG. 4, thethermal crown R caused by a thermal expansion change of a roll changesgradually in an area “S” between the center of the strip and thevicinity of the strip end E, but changes dramatically in the areas “a”and “b” (before and after the strip edge). In the area “T” between thestrip end and the roll end, the thermal crown R gradually changes again.The gradual thermal crown change in the area “S” can be controlled fullyby a conventional roll bender or the like and it matters little. Thethermal crown change in areas “b” and “T” are outside the strip and canbe ignored as it will not directly give any influence to the strip.Therefore, the most-concerned thermal crown to be controlled is that inthe area “a” and the quantity of a thermal crown which substantiallyaffects the thickness of the strip us “Cs” in FIG. 4. Usually, “Ch” inFIG. 4 is adopted as the quantity of a thermal crown because thequantity is measured relative to the end of the roll end, assuming that“Ch” is approximately equal to 2 times of “CS.” In the descriptionbelow, the length of the area “a” (relative to the end of the strip) iscalled a thermal influence length. This thermal influence length issteadily 100 mm to 300 mm as disclosed by “Plasticity and Working”Vol.23, No.263 (December, 1982), although it is dependent upon therolling period, rolling condition, coolant control method, etc. It isapparent that, when a strip is rolled by the working rolls having such athermal crown, the rolled strip will have edges much thicker than anyother part of the strip. (Edge-up phenomenon)

[0117] The object of the present invention is to control such a thermalcrown. For that purpose, the present invention provides a locallyconcave crown 2 a on one end of each working roll 2 as explained above.

[0118] In addition to said local convex crows 2 a, the present inventionprovides a first shape control means which controls a thermal crownformed on the working rolls 2 together with the local convex crows 2 aand a second shape control means which controls so that the stripmaterial 1 may has at least a convex crown in the center of the strip.In the embodiments of the present invention, the first shape controlmeans is the decremental bending equipment 10 b (decremental bender)which works to narrow the gap between one pair of upper and lowerworking rolls and the second shape control means is the incrementalbending equipment 11 a (incremental bender) which works to control thebending of one pair of upper and lower intermediate rolls 3.

[0119] Below will be explained a rolling method by the rolling mill inaccordance with the present invention.

[0120] To control a thermal crown by the working rolls 2 each of whichhas a locally concave crown 2 a at the end of the roll, the workingrolls 2 are shifted to a proper position according to the thermal crownwhich is generated. However, it is very hard to detect the thermal crownaccurately while rolling is in progress. So shape detectors (see FIG. 19and FIG. 20) are provided on the side of the output of the rolling milland the output of the shape detectors are used for controlling. It isnot preferable particularly in aluminum rolling to shift said workingrolls 2 during rolling. Therefore it is recommendable to shift theworking rolls properly when rolling is not in progress (e.g. rollingcoils are exchanged) or when a slow rolling is in progress (e.g. at theexchange of rolling paths). Thanks to the effect of the local concavecrowns, the influence by the thermal crown on the working rolls 2 can bereduced directly.

[0121] However, the thermal crown on the working rolls change everymoment. This ever-changing thermal crown can be controlled by the firstshape control means of the working roll bender, particularly, adecremental bender which controls the bending of the working rolls andthe second shape control means (the incremental bender 11 a for theintermediate rolls 3) which controls to give a convex crown to the stripmaterial 1. The major point of this rolling method is to control, forexample, the first shape control means to decrease the gap between theworking rolls and the second shape control means to increase accordingto the quantity of the detected thermal crown during rolling so that theshape control means may work oppositely on the strip material.Naturally, it is needless to say that, when the thermal crown is reducedby a roll coolant control or the like, said first shape control means iscontrolled to increase and the second shape control means is controlledto decrease. The object of this method is to eliminate the change in thecentral thickness of the strip caused by the first shape control meansby controlling the second shape control means to cancel the effect bythe first shape control means. This enables optimum rolling withoutdisturbing the flatness of the strip by the operation of the fist shapecontrol means. Particularly, by determining the quantity of operation ofthe first shape control means according to the shape output from nearthe strip edges and the quantity of operation of the second shapecontrol means according to the shape output from the center of thestrip, it is possible to explicitly classify the target operation valuesof the first and second shape control means. This makes actual controlmethods extremely more comprehensive and easier. Further, to make theabove control more effective, the preferable diameter of the workingroll should satisfy the conditions expressed by Formula (3).

[0122] An example of simulation of controlling thermal crown shapes inrolling will be explained below under the conditions given in Table 1.This example assumes rolling of a strip of 1200 mm wide. TABLE 1Interme- Strip Strip Working diate Backup thicknes thicknes Linear rollroll roll Roll s before s after rolling diameter diameter diameterlength rolling rolling pressure (mm) (mm) (mm) (mm) (mm) (mm) (mm) 400470 1200 1400 0.5 0.3 0.32

[0123]FIG. 5 is an explanatory illustration of the dimensions of localcrowns of the working rolls and the intermediate rolls and shifting ofrespective rolls. In FIG. 5, Lcw and Lci are respectively the distancebetween the start of a crown and the end of the working roll 2 and thedistance between the start of a crown and the end of the intermediateroll 3. Lcw and Lci are respectively 168 mm. Cw and Ci are respectivelythe quantity of a crown on the working roll end and the quantity of acrown on the intermediate roll end and 40μ in quadratic curves). δw andδi are respectively the distance between the strip edge 1 and the end ofthe working roll and the distance between the strip edge 1 and the endof the intermediate roll.

[0124]FIG. 6 shows the shapes of thermal crowns given in the presentsimulation. The curves A, B, and C are respectively for thermal crownsof 60μ, 50μ, and 40μ. The thermal influence length is approximately 175mm.

[0125]FIG. 7 shows the result of simulation of rolling by a 6-highrolling mill using straight rolls having no local crowns underconditions of the above thermal crowns. The horizontal axis of FIG. 7represents the distance relative to the center of the strip (inmillimeters) and the vertical axis represents the thickness of therolled strip (in millimeters). Assuming that the distance (δi) betweenthe strip edge and the end of the intermediate roll is 0, the bendingforces Fw (by the working roll bender) and Fi (by the intermediate rollbender are respectively −18 tons (“−” means “decremental”) and 68 tonsso that the body crown in the center of the strip may be approximatelylinear (flat). Curves A, B, and C in FIG. 7 are respectively for thermalcrowns 60μ, 50μ, and 40μ in that order.

[0126] As apparent from FIG. 7, every case has an extreme increase inthickness near strip edges (called “edge-up shapes”) as shown by EA ofcase A. Further, it is apparent that the strip thickness temporarilyfalls extremely just before the edge-up starts (edge 2 indicated by ES).This so-called edge 2 elongation which is locally extended near the edge2 exerts an internal pulling force (internal tension) on the edge-upstrip edges. An external force such as a tension by the take-up reelalso works strongly near the edges and is added to the above internaltension. These strong forces are enemies to thin silicon steel strips(of 0.3 mm thick or under) even in the cold reversible rolling and moreparticularly to soft aluminum or copper strips. They may easily breakthe strips in rolling as already explained above.

[0127] Below will be explained whether such shapes can be improved onlyby adjustment of the bending force. Here, the effect which theintermediate roll bender Fi exerts on the whole width of the strip andvalid to control the body crown, but not valid to control shapes whichappear only near strip edges. So we simulated how the shapes arecontrolled by changing the working roll bender Fw only. FIG. 8 shows theresult of the simulation, assuming that a thermal crown is 50μ (as wellas characteristic curve B of FIG. 7). The characteristic curve “a” isfor Fw of 14 tons and the characteristic curve “b” is for Fw of 22 tons.As for the curve “a” the edge 2 elongation decreases when the bendingforce Fw increases, but the edge-up shape increases. Therefore, it isapparent that the shape and the tension distribution cannot be improvedby increase of Fw. Contrarily, when Fw is decreased, the edge-up shapeis a little improved and the body crown becomes bigger and the stripshape is not acceptable.

[0128] Judging from the above, controlling only by the normal rollbender almost ineffective to the local irregularity near the stripedges.

[0129] Next, we simulated rolling by giving local concave and convexcrowns to the end of the working rolls and the intermediate rolls. Theresult of the simulation is illustrated in FIG. 9. In this case, theroll shifts δw and δi are respectively 14 mm and 0 mm in that order.Characteristic curves A, B, and C are respectively for thermal crowns60μ, 50μ, and 40μ in that order. The bending forces are properlyadjusted to have a good strip flatness.

[0130] As apparent from FIG. 9 and FIG. 7 in comparison, the edge-upshape by a thermal crown of a current interest is greatly improved.Therefore, when this example is applied to a cold reversible rollingfacility or a rolling facility for soft materials such as aluminum orcopper, the operability, yield, and quality of rolling products will beimproved dramatically.

[0131] Referring to FIG. 10, below will be explained an effect of givinga local convex crown to the ends of intermediate rolls 3. FIG. 10 showsthe distributions of linear contact pressures before and after localconvex crowns are applied to the ends of the intermediate rolls 3,assuming a thermal crown of 50μ is applied. The curve Q indicates thedistribution of linear contact pressures between the working roll 2 andthe intermediate roll 3 and the curve R indicates the distribution oflinear contact pressures between the intermediate roll 3 and the backuproll 4. However, the roll bending forces are a little changed to matchthe crown of the rolled strip with the characteristic curve B of FIG. 9.FIG. 9 also shows the shape of the resulting body crown S for reference.

[0132] As seen from FIG. 10, when a local convex crown is applied, thepeak in the linear pressure distribution on the ends of the rolls (seethe curve D) is decreased greatly. So it is apparent that giving a localconvex crown to the ends of the intermediate rolls 3 has the effect tosuppress uneven abrasion of respective rolls and make the service livesof the rolls longer. However, it is apparent that the local convex crownof the intermediate rolls 3 are not necessary and absolute conditionsjudging from the shape control characteristics of thermal crowns becausethe resulting flatness (shapes) are almost identical. For example, incase the rolling load is small and the roll contact surface pressure isignorable, the local convex crowns on the intermediate rolls 3 areomittable.

[0133] It is needless to say that the thermal crown changes every timeeven in rolling of an identical coil. For example, in rolling underconstant coolant control conditions, the thermal crown is apt toincrease gradually. Contrarily, when the working rolls are given localconcave crowns, the position of the working rolls 2 must be controlledevery time according to the quantity of thermal crowns. However, movingthe working rolls during rolling may possibly give flaws to the rolledsurfaces and it is not preferable to move the working rolls duringrolling in the cold rolling facility, particularly in rolling of softmaterials such as aluminum. It is also possible to control the thermalcrowns by coolant control, but this is very slow to answer and notpractical.

[0134] Therefore, the present invention uses the roll bender controlmethod to control the change of thermal crowns in rolling. In this case,as seen from FIG. 9, it is necessary to control the working roll benderto narrow the gap between rolls and the intermediate rolls to increasethe gap as the thermal crown increases. In this case, if a greater localconcave crown is applied to the working rolls, the working roll bendercan be controlled to increase, but in this case the edge drop willincrease. Therefore, it is preferable to make the local concave crown assmall as possible. Further, controlling the thermal crowns by both thelocal concave crowns and the decremental bender can increase the yieldof products greatly.

[0135] Further when the above control is accompanied by a roll bendercontrol, the setting of the position of the working rolls 2 need not beso fine. See FIG. 11 which is the result of simulation representing therelationship between the shift position setting and the shape controlcharacteristics, using the same conditions as those for Table 1 and athermal crown of 50μ. Curves A, B, and C in FIG. 11 are respectively forroll shifts (δw) 0 mm, 14 mm, and 28 mm in that order. They are thedistributions of the rolled strip thickness with the working roll benderand the intermediate roll bender adjusted properly.

[0136] As apparent from FIG. 11, preferable rolling shapes can beobtained by controlling the bending forces of the working rolls 2 andthe intermediate rolls 3 even when the setting position of the workingrolls is changed. Contrarily the use of both the working roll bender andthe intermediate roll bender enables a rough setting of the working rollpositions. The above effect by the use of both roll benders is apparentand greatly simplifies the setting of the shifting position of theworking rolls 2.

[0137] In this thermal crown control, the diameter of each working rollsubstantially has significant meanings. In other words, the body crowncaused by the thermal crown can be approximately expressed by apolynominal of the fourth order or higher. Therefore, the work roll'scharacteristics affecting the body crown preferably have components oforders as high as possible. This means the diameter of each working rollis preferably small. However, if the diameter of the working roll isextremely small, the effect of the roll benders is limited to the stripedges and their vicinity which is smaller than the thermal influencelength of the thermal crown. Accordingly, this does not have anysubstantial merit to control the thermal crown. Further, the smallworking roll diameter may disable driving of the working rolls which isrequired for steady rolling. This is one of significant points to benoticed in installation of a cold reversible rolling facility whichrolls soft materials such as aluminum and copper. Further, if thediameter of the working roll is small, the body crown created by theworking roll bender generally becomes complicated. This makes shapecontrolling more difficult. Contrarily, when the diameter of the workingroll is great, low-order components will be predominant when the workingroll bender exerts on the body crown. Therefore, when a thermal crown iscontrolled, the body crown is affected greatly and the control is farfrom the optimum one.

[0138] Judging from the above, for control of a thermal crown by boththe working roll benders having local concave crowns on the ends and theworking roll bender, it is apparent that the optimum diameters of theworking rolls enter in a certain range. This will be explained belowreferring to FIG. 12.

[0139]FIG. 12 shows the characteristics of the working roll decrementalbender exerting on the body crown, having the diameter of the workingroll as the horizontal axis and the rate “r” of high-order components ofthe body crown as the vertical axis. “r” is expressed by

r=a ₄/(a ₂ +a ₄)  (1)

[0140] wherein “a₂”, and “a₄”, are coefficients of a 4-order polynominaloptimizing the change “δCw” of the body crown by the working rollbending force “δFw.”

δCw=a ₄ X ⁴ +a ₂ X ²  (2)

[0141] wherein “x” is the X coordinate of the strip edge (±1) relativeto the center of the rolling mill.

[0142] In other words, “r” is the ratio of a high-order component “a₄”to the whole amount of body crowns “a₄+a₂” appearing on strip edges bythe bending force “δFW.” As this “r” value increases, the high-ordercomponent has a greater effect that the working roll bender exerts onthe body crown. That is, a greater “r” value is best fit for thermalcrown controlling. Curves A, B, and C in FIG. 12 are respectively formaximum strip widths 1200 mm, 1500 mm, and 1800 mm. In this case, therolls are respectively 1420 mm, 1720 mm, and 2020 mm long and the linearrolling pressure (load) is 0.5 ton/mm.

[0143] As apparent from FIG. 12, even when the diameter of the workingroll is equal to or greater than the “a” value in the figure, thehigh-order component fit to control a thermal crown changes little.Contrarily, it increases the rolling load and power, the size of therolling mill, and consequently the rolling cost. For effective thermalcrown controlling, it is particularly preferential to use working rollswhose diameter is equal to or greater than the “a” value given in FIG.12.

[0144] Further, when the diameters of the working rolls are smaller, theratio “r” of the high-order component of the body crown is 1 or above.FIG. 13 shows an example of calculating the change “δCw” of the bodycrown, assuming the diameter of the working roll is 200 mm and themaximum strip width is 1200. The solid line represents an approximateline obtained from the approximate equation of “δCw” (given in FIG. 13).From FIG. 13, we can see that the change “δCw” that the force “δFw”exerts on the body crown shows a complicated characteristic which makesa concave form in the center of the strip. Therefore, the approximateequation of the change of the body crown “δCw” is made so that thefourth and second order coefficients have different signs andconsequently the ratio of the high-order component becomes “r” or above.If the working roll bender of a rolling mill having such characteristicsis controlled to decrease, the strip edges can be thinner. The center ofthe strip has an effect as if the incremental bender is applied. This isa very complicated characteristic, which makes actual shape controlcomplicated. This must be avoided. Therefore the work roll diameter mustbe selected so that the ratio of the high-order component may be 1 orless.

[0145] Substantially, it does not mean that the smaller roll diameter isdetermined only from said shape control characteristics and it isnatural that the roll diameter is such as to transmit required rollingtorque.

[0146] In summary, FIG. 14 shows preferable ranges of working rolldiameters most suitable to control thermal crowns using both the localconvex crown rolls and roll benders. FIG. 14 has the maximum strip widthas the horizontal axis and the roll diameter as the vertical axis. Thepreferable working roll diameter Dw in FIG. 14 is expressed by

⅙Wm+50≦Dw≦⅙Wm+250  (3)

[0147] wherein Wm is the maximum strip width.

[0148] The embodiment of the present invention can control thermalcrowns in cold rolling without causing any flaw in the rolled surfacesand any response problems, further can properly control thermal crownswhich change every moment in rolling without deteriorating the wholestrip shape. Thus, the present embodiment can produce steady rolledproducts.

[0149] Next will be explained another embodiment using the other type ofrolling mill having the similar effect.

[0150]FIG. 15 shows a 6-high rolling mill which is another embodiment ofthe present invention. This embodiment has working rolls each of whichhas a local concave crown at one end of the roll and the working rollsare disposed vertically symmetrically with a point. The working rollscan be shifted horizontally. Similarly the intermediate rolls 3 arestraight rolls which can be shifted horizontally. When controlling athermal crown, the working rolls 2 are shifted so that each strip edgemay come on the locally convex crown 2 a of each working roll 2. Furtherthe intermediate rolls 3 are disposed so that its end may beapproximately near one of the strip edges. Naturally, the upper andlower rolls 2 and 3 are disposed approximately symmetrically with apoint.

[0151] From the aforesaid description, it is apparent that the rollingmill in accordance with the present invention can preferentially controlthermal crowns on the local concave crown 2 a of the working rolls 2more together with the use of a working roll bender or particularlytogether with the decremental bender. However, as the intermediate rolls3 have no escape for the local concave crown 2 a, the linear contactpressure between rolls increases. But there is another merit to use therolling mill of this type for thermal crown controlling.

[0152] Even when there is no thermal crown, the intermediate rollsrequire a basic bending force (so-called basic intermediate roll bendingforce) to control a body crown caused by a bending of rolls such as thebackup rolls. Contrarily, the rolling mill such as that of FIG. 15 canmake the width of contact between the working roll and the intermediateroll approximately equal to the strip width. In other words, this canmake the width of a load distributed between the working roll and theintermediate roll approximately equal to the strip width and the workingrolls 2 outside the strip width undergo no extra force. Consequently,the bending of the working rolls 2 decreases. This has an effect toreduce said required basic intermediate roll bending force and furtherto reduce the linear contact pressure caused by the intermediate rollbender between the intermediate roll 3 and the backup roll 4.

[0153] In the description of FIG. 9, we explained that the intermediateroll bending force is controlled to increase as the thermal crownincreases. As said basic intermediate roll bending force is added tothis intermediate roll bending force, the effect of using the rollingmill of the present structure is apparent when both the local concavecrown rolls and the roll bending equipment are used to control thermalcrowns. Particularly, the rolling mill of the present structure iseffective for rolling of a narrow strip when the strip width range iswide (for example when the minimum strip width is 0.4 to 0.3 of themaximum strip with).

[0154] In the above embodiment description, we explained a 6-highrolling mill comprising intermediate rolls 3 which can be shiftedhorizontally and working rolls 2 each of which has a local concave crownat its end. We also explained that using the roll bender together iseffective for controlling a change of a thermal crown in rolling. Themain feature of this thermal crown controlling using bender controllingtogether in the 6-high rolling mill is using a working roll bender whichis a first shape control means fit to control a thermal crown whichgenerates on the working rolls 2 and a second shape control means fit tocontrol body crowns which are caused by a bending of rolls such as thebackup rolls 4. In other words, to control thermal crowns, the firstshape control means is controlled to decrease and the second shapecontrol means is controlled to increase so that the convex body crownmay be suppressed and the rolled strip has an even flatness over thefull width of the strip.

[0155] We have another method of controlling thermal crowns which changeevery moment in rolling. This method mainly comprises a step of shiftingeach the intermediate rolls 3 of the 6-high rolling mill having theshiftable intermediate rolls of FIG. 1 away from each strip edge insteadof using the working roll bender (working as the first shape controlmeans) together to control the change of thermal crowns in rolling. Withthis, the end part of each intermediate roll 3 presses the local concavecrown on the end of each working roll 2 and gives a local bendingdeformation to the end part of the working roll 2. This further pressesthe edges of the strip. It is needless to say that the pressing force atthe strip edges can be reduced by shifting the intermediate rolls 3towards the center of the strip. This method does not shift the workingrolls during rolling and causes no flaw on the rolled surfaces.Therefore, this method can effectively control ever-changing thermalcrowns.

[0156] In the above embodiments, the second shape control means of the6-high rolling mill is an intermediate roll bender. Various methodsexplained below will be applicable to the second shape control means.

[0157]FIG. 16 shows a schematic sectional view of a cross-shift type4-high rolling mill which is one of the embodiments of the presentinvention. This rolling mill has a shifting means which can shift theworking rolls 2 horizontally and a crossing means which can rotate theworking rolls around the vertical center of the rolling mill. Typicalcrossing and shifting means are disclosed in Japanese Non-examinedPatent Publication No.7-60310 (1995).

[0158] A local concave crown is formed on one end of each working roll2. The rolling mill has at least a decremental bender or preferably botha decremental bender and an incremental bender as a first shape controlmeans. It is publicly known that the cross-movement of the working rolls2 can vary the gap (so-called a roll gap) between the upper and lowerworking rolls 2 along the width of the rolled strip almost quadraticallyand effective to control body crowns. Therefore, in this case, thesecond shape control means is the crossing means of the working rolls 2.FIG. 16 shows an example of crossing the working rolls 2, but it isapparent that the similar effect is obtained by using a crossing means,as the second shape control means, which crosses only the backup rolls 4or both the working rolls 2 and the backup rolls 4 simultaneously.Further, a 6-high rolling mills comprising intermediate rolls with acrossing means such as disclosed in Japanese Non-examined PatentPublication No.10-234512 (1998).and Japanese Non-examined PatentPublication No.2000-33405 can use the intermediate rolls crossing meansas the second shape control means.

[0159]FIG. 17 shows a schematic sectional view of a 6-high rolling millwhich is another embodiment of the present invention. The working rolls2 each of which has a local concave crown on one end of the roll can beshifted horizontally. The rolling mill has at least a decremental benderor preferably both a decremental bender and an incremental bender as afirst shape control means.

[0160] Each of the intermediate rolls is profiled to have a tertiarycurve with maximum and minimum points and shifted horizontally by asecond shape control means. It is publicly known that the gap betweenthe upper and lower working rolls 1 can be controlled substantiallyquadratically by shifting the intermediate rolls by said second shapecontrol means and effective to control body crowns. However, said secondshape control means has almost no effect to control local irregularitieson strip edges such as thermal crowns. Thus the first shape controlmeans is required.

[0161]FIG. 18 shows a schematic sectional view of a 4-high rolling millwhich is another embodiment of the present invention. The working rolls2 each of which has a local concave crown on one end of the roll can beshifted horizontally. The rolling mill has at least a decremental benderor preferably both a decremental bender and an incremental bender as afirst shape control means. The backup rolls 4 respectively have a convexcrown which is gradually tapered from the center of the roll to the endof the roll and are shifted by a shifting means. It is publicly knownthat the gap between the upper and lower working rolls 1 can becontrolled substantially quadratically by shifting the intermediaterolls 4 vertically by said second shape control means and effective tocontrol body crowns. For example, said working rolls with said crownsand said shifting means are disclosed in Japanese Patent PublicationNo.2865804. In this case, the second shape control means is a shiftingmeans for the backup rolls 4. In such a rolling mill, it is preferablethat the local concave crown of the working roll 2 is matched with theconvex crown of the backup roll 4. This has an effect of reducing thecontact surface pressure between the working roll 2 and the backup roll4 and an effect of eliminating inclined abrasion of rolls, which isapparent from the above description of the 6-high rolling mill.

[0162]FIG. 19 is a schematic illustration of a reversible steel rollingsystem to which an embodiment of the present invention is applied. Thisrolling system comprises a rolling mill 17 in the center of the system,tension reels 19 (one each side of the rolling mill), pinch rolls 20(one pair each side of the rolling mill), shape detectors 21 (one eachside of the rolling mill), fluid cutting means 22 (one pair each side ofthe rolling mill), a pay-off reel which feeds the first strip material(coil) (only one side of the rolling mill), and another set of pinchrolls 20 (only one side of the rolling mill). Further, the rolling mill17 has roll cooling headers 23 and lubricant headers 24 at each side ofthe rolling mill. The strip material 1 is fed and taken up between thetension reels 19 to be rolled repeatedly. Terms “IN” and “OUT” in thedescription below respectively represent the entrance side of therolling mill 17 to which the strip material 1 is supplied and the exitside of the rolling mill 17 from which the strip material 1 is ejected.

[0163] Initially, the strip material 1 is placed on the pay-off reel 18,taken out and guided by pinch rolls 20, and transferred into the rollingmill 17. In the rolling mill 17, the coolant headers 23 and thelubricant headers 24 apply fluid to the working rolls 2 and the areas(roll bytes) where the working rolls 2 touch the strip material 1 tocool and lubricate them during rolling. The rolled strip is taken up bythe OUT tension reel 19. The roll cooling fluid and the lubricatingfluid are usually the same fluid and hereinafter they will be calledsimply as coolant. (oil). Said coolant oil is not fed from the OUT sprayheaders 23 and 24. This is because any remaining oil on the stripsurface may increase the possibility of coil slippage, skewing anduncoiling of the reel 19. A fluid cutting means 22 are provided toremove the coolant oil almost completely However, complete removal ofthe fluid is very difficult and the possibility of coil slippage,skewing and uncoiling of the reel 19 will be greater if the rolledmaterial has an edge-up due to thermalcrown (as explained already).Further, this possibility increases more in the cold reversible rollingfacility that moves the strip forward and backward by the IN and OUTtension rolls to roll repeatedly. Usually, when a great edge-up shape isfound by the OUT shape detector 21, the rolling is carried out carefully(e.g., by slowing down the rolling rate).

[0164] From the above description, we find that thermal crowncontrolling by a cold reversible rolling mill in accordance with thepresent invention will have a striking effect to increase rolled surfacequalities, yields, and productivity of rolling.

[0165]FIG. 20 is a schematic illustration of an aluminum rolling systemto which an embodiment of the present invention is applied. Unlike thegeneral reversible rolling system for steel strips, this aluminumrolling system employing a one-way rolling method has a tension reel 19only in the OUT side and a pay-off reel 18 in the IN side. Usually theone-way rolling method repeatedly rolls dozens of coils as one unit. Inother words, each coil is placed on the pay-off reel 18, fed into therolling mill, and taken out by the tension reel 19. Dozens of coils in aunit are rolled through in sequence for one path at a time and thenrolled repeatedly for the next and later paths until the target stripthickness is obtained. As explained above, this rolling method does nottransfer any coil from the tension roll to the pay-off reel and requiresno shape detector 21 in the IN side and no coolant header 23 and 24 inthe OUT side.

[0166] In the one-way rolling as in the aluminum rolling mill, theleading and trailing ends of each coil are always rolled without beingtensioned in each rolling path. Without a tension, the coil is apt tohave meanders in the leading and trailing parts of the coil. Thistendency becomes greater as the coil is rolled thinner (towards thetarget thinness). To suppress such meanders, it is preferable to removeany factor such as a thermal crown that causes a disturbance. In thissense, it is very significant to apply, to aluminum rolling, the rollingmills in accordance with the present invention which has a high abilityto control thermal crowns.

[0167] As already explained, the aluminum rolling system using coolantoil of a low flashing point is likely to cause a fire at a break of thecoil. One of the main coil break causes is an edge-up phenomenon due toa thermal crown as already explained. Particularly, soft materials suchas aluminum are affected by thermal crowns and likely to be broken inrolling. Usually, such a rolling system 17 is placed in a largefire-extinguishing system (not visible in FIG. 18) for quick fireextinguishing. However, once a fire breaks, many parts such as oilseals, flexible hoses, and wires may be seriously damaged even when itis extinguished immediately. It will require huge repairing money andtime. Therefore, it is very significant to control thermal crownseffectively in aluminum rolling systems, to reduce the possibility offire, and consequently to improve the operability and productivity ofrolling.

[0168] The present invention enables stable production of high-qualitycold rolling products, controlling the ever-changing thermal crownsduring rolling without causing any flaws in the rolled surfaces and withquick responses to ever-changing thermal crowns.

What we claim is:
 1. A cold rolling mill of at least four-high ormore-than-4-high comprising first shifting equipment which can shift apair of upper and lower working rolls in opposite directions and rollbending equipment which controls the bending of said pair of workingrolls, wherein said cold rolling mill further comprises locallygradually-thickened-toward-end parts provided on said working rolls atone ends thereof so as to be symmetrical with respect to a point, afirst shape control means for controlling a thermal crown formed on eachof said pair of working rolls together with said locallygradually-thickened-toward-end parts, and a second shape control meansfor controlling to form a concave crown in the center of said rolledmaterial.
 2. A cold rolling mill in accordance with claim 1, whereinsaid roll bending equipment comprises decremental bending equipment andsaid first shape control means is said decremental bending equipment. 3.A cold rolling mill in accordance with claim 1, wherein said rollingmill is a 6-high mill comprising a pair of upper and lower intermediaterolls and a second shifting equipment which can rotate said pair ofupper and lower intermediate rolls in opposite directions, said firstshape control means is said second shifting equipment.
 4. A cold rollingmill of at least four-high or more-than 4-high comprising first shiftingequipment which can shift a pair of upper and lower working rolls inopposite directions and roll bending equipment which controls thebending of said pair of working rolls, wherein each of said upper andlower working rolls has a locally gradually-thickened-toward-end part inwhich the diameter increases toward one end of the working roll, saidlocally gradually-thickened-toward-end parts are disposed verticallysymmetrically with respect to a point, said roll bending equipment asthe first shape control means comprises decremental bending equipmentwhich works to narrow the gap between said pair of upper and lowerworking rolls, and said rolling mill further comprises a second shapecontrol means for controlling to form a concave crown in the center ofsaid rolled material.
 5. A cold rolling mill of at least 4-high ormore-high for a cold reversible rolling facility comprising firstshifting equipment which can shift a pair of upper and lower workingrolls in opposite directions and roll bending equipment which controlsthe bending of said pair of working rolls, wherein each of said upperand lower working rolls has a locally gradually-thickened-toward-endpart which increases its diameter on one end of the working roll, saidlocally gradually-thickened-toward-end parts are disposed verticallysymmetrically with respect to a point, said roll bending equipment asthe first shape control means comprises decremental bending equipmentwhich works to narrow the gap between said pair of upper and lowerworking rolls, and said rolling mill further comprises a second shapecontrol means for controlling to form a concave crown in the center ofsaid rolled material.
 6. A cold rolling mill of at least four-high ormore-high for a cold aluminum rolling facility comprising first shiftingequipment which can shift a pair of upper and lower working rolls inopposite directions and roll bending equipment which controls thebending of said pair of working rolls, wherein each of said upper andlower working rolls has a locally gradually-thickened-toward-end part inwhich the diameter increases on one end of the working roll, saidlocally gradually-thickened-toward-end parts are disposed verticallysymmetrically with respect to a point, said roll bending equipment asthe first shape control means comprises decremental bending equipmentwhich works to narrow the gap between said pair of upper and lowerworking rolls, and said rolling mill further comprises a second shapecontrol means for controlling to form a concave crown in the center ofsaid rolled material.
 7. A cold rolling mill in accordance with any ofclaims 1 and 4 to 6, wherein said rolling mill is a 6-high millcomprising a pair of upper and lower intermediate rolls which can moveaxially and said second shape control means is equipped with anincremental bending equipment which controls the bending of said pair ofintermediate rolls.
 8. A cold rolling mill in accordance with claim 7,wherein each of said pair of upper and lower intermediate rolls have alocally tapered part on the side where thegradually-thickened-toward-end part exists so that the tapered part maybe engaged with said gradually-thickened-toward-end part of each workingroll and the rate of diameter changing of said tapered part is equal toor greater than the rate of diameter changing of thegradually-thickened-toward-end part.
 9. A cold rolling mill inaccordance with any of claims 1 and 4 to 6, wherein said rolling mill isa 6-high mill comprising a pair of upper and lower intermediate rollseach of which has a curved roll crown containing both a maximum and aminimum all over the roll and said second shape control means hasshifting equipment which shifts said pair of upper and lowerintermediate rolls in opposite directions.
 10. A cold rolling mill inaccordance with any of claims 1 and 4 to 6, wherein said rolling mill isa 6-high mill comprising a pair of upper and lower intermediate rollswhich can move axially and said second shape control means has aroll-crossing mechanism which tilts at least said pair of intermediaterolls horizontally with the center of the mill approximately as thecenter of rotation.
 11. A cold rolling mill in accordance with any ofclaims 1 and 4 to 6, wherein said rolling mill is a 4-high rolling milland said second shape control means is equipped with a roll-crossingmechanism which tilts said pair of working rolls or one pair of rollssupporting said working rolls with the center of the mill approximatelyas the center of rotation.
 12. A cold rolling mill in accordance withany of claims 1 and 4 to 6, wherein said rolling mill is a 4-high mill,each of said pair of supporting rolls for supporting said working rollshas a roll crown which is tapered from about the center of the rolltowards one end of the roll, said roll crowns are disposed verticallysymmetrically with respect to a point, and said second shape controlmeans is equipped with the shifting equipment which can move saidsupporting rolls in different directions.
 13. A cold rolling mill inaccordance with any of claims 1 and 4 to 6, wherein the diameter of eachof said upper and lower working rolls is expressed by ⅙Wm+50≦Dw23⅙Wm+250 wherein Dw is the diameter of each of the working rolls and Wmis the maximum width of a sheet to be rolled.
 14. A cold rolling millcomprising: a pair of working rolls each provided with a roll-contourshape having a portion thickened-toward-end which increases in diametertoward a roll end in the vicinity of the roll end on one end side of aroll barrel portion thereof, said working rolls being arranged so thatsaid thickened-toward-end portions are positioned at places on theopposite sides of the barrel portions in the roll axis direction;intermediate rolls supporting said working rolls, respectively; a rollbending device for applying roll bending force on said working rolls;and an intermediate roll bending device for applying roll bending forceon said intermediate rolls.
 15. A cold rolling mill comprising: a pairof working rolls each, provided with a roll-contour shape having aportion thickened-toward-end which increases in diameter toward a rollend in the vicinity of the roll end on one end side of a roll barrelportion thereof, and rolling rolling materials, said working rolls beingarranged so that said thickened-toward-end portions are positioned atplaces on the opposite sides of the barrel portions in the roll axisdirection; intermediate rolls supporting said working rolls,respectively; backup rolls supporting said intermediate rolls,respectively; a roll bending device for applying roll bending force onsaid working rolls; and an intermediate roll crossing mechanism forcrossing the roll axes of said intermediate rolls in a horizontal planeagainst a perpendicular direction to the rolling material travelingdirection, or a roll shifting device for shifting said intermediaterolls along the roll axis direction.
 16. A cold rolling mill comprising:a pair of working rolls each provided with a roll-contour shape having aportion thickened-toward-end which increases in diameter toward a rollend in the vicinity of the roll end on one end side of a roll barrelportion thereof, said working rolls being arranged so that saidthickened-toward-end portions are positioned at places on the oppositesides of the barrel portions in the roll axis direction; supportingrolls supporting said working rolls, respectively; a roll bending devicefor applying roll bending force on said working rolls; and a supportingroll shifting device for shifting said supporting rolls along the rollaxis direction.
 17. A cold rolling mill comprising: a pair of workingrolls each, provided with a roll-contour shape having a portionthickened-toward-end which increases in diameter toward a roll end inthe vicinity of the roll end on one end side of a roll barrel portionthereof, and rolling rolling materials, said working rolls beingarranged so that said thickened-toward-end portions are positioned atplaces on the opposite sides of the barrel portions in the roll axisdirection; supporting rolls supporting said working rolls, respectively;a roll bending device for applying roll bending force on said workingrolls; and a roll crossing mechanism for crossing the roll axes of saidworking rolls in a horizontal plane against a perpendicular direction tothe rolling material traveling direction.
 18. A rolling method whichcomprises the steps of: using shape detectors which measure the shapesof a sheet at least after being rolled and a 4-high or more-high coldrolling mill which comprises shifting equipment which can shift one pairof upper and lower working rolls each of which has a locallygradually-thickened-toward-end part on one end of respective workingrolls with the locally gradually-thickened-toward-end parts disposedvertically symmetrically with respect to a point, roll bending equipmentwhich controls bending of said pair of working rolls and has, as a firstshape control means, decremental bending equipment which works to narrowthe gap between said pair of working rolls, and a second shape controlmeans for forming a concave crown in the center of said rolled material,adjusting the position of said one pair of upper and lower working rollsby said shifting equipment so that side edges of the rolled sheet may belimited by said gradually-thickened-toward-end parts of said workingrolls before starting rolling, approximately fixing the shift positionof said pair of upper and lower working rolls while rolling is inprogress, and determining the operations of said first and second shapecontrol means so that their effects on the sheet may work reverselyaccording to the output of said shape detectors.
 19. A rolling method inaccordance with claim 18, wherein the operation of said first shapecontrol means is determined according to the output of said shapedetector placed near the edge of the sheet and the operation of saidsecond shape control means is determined according to the output of saidshape detector placed near the center of the sheet.
 20. A rolling methodwhich comprises the steps of: using shape detectors which measure theshapes of a sheet at least after being rolled and a 6-high cold rollingmill which comprises first shifting equipment which can shift one pairof upper and lower working rolls each of which has a locallygradually-thickened-toward-end part on one end of respective workingrolls with the locally gradually-thickened-toward-end parts disposedvertically symmetrically with respect to a point, second shiftingequipment which can rotate one pair of upper and lower intermediaterolls which support said working rolls reversely, and a second shapecontrol means for forming a concave crown in the center of said rolledmaterial, adjusting the position of said one pair of upper and lowerworking rolls by said first shifting equipment so that side edges of therolled sheet may be limited by said gradually-thickened-toward-end partsof said working rolls before starting rolling, approximately fixing theshift position of said pair of upper and lower working rolls whilerolling is in progress, and determining the operations of said secondshifting equipment and said shape control means according to the outputof said shape detectors.
 21. A rolling method in accordance with claim20, wherein the operation of said second shifting equipment isdetermined according to the output of said shape detector placed nearthe edge of the sheet and the operation of said shape control means isdetermined according to the output of said shape detector placed nearthe center of the sheet.
 22. A rolling method of a cold rolling millcomprising a pair of working rolls each, provided with a roll-contourshape having a portion thickened-toward-end which increases in diametertoward a roll end in the vicinity of the roll end on one end side of aroll barrel portion thereof, said working rolls being arranged so thatsaid thickened-toward-end portions are positioned at places on theopposite sides of the barrel portions in the roll axis direction,intermediate rolls supporting said working rolls, respectively, andbackup rolls supporting said intermediate rolls, respectively, whereinsaid method comprises the steps of controlling thermal crown duringrolling by applying roll bending force on said working rolls, andcontrolling body crow at a central portion of the plate depth byapplying roll bending force on said intermediate rolls.
 23. A rollingmethod of a cold rolling mill comprising a pair of working rolls each,provided with a roll-contour shape having a portion thickened-toward-endwhich increases in diameter toward a roll end in the vicinity of theroll end on one end side of a roll barrel portion thereof, said workingrolls being arranged so that said thickened-toward-end portions arepositioned at places on the opposite sides of the barrel portions in theroll axis direction, intermediate rolls supporting said working rolls,respectively, and backup rolls supporting said intermediate rolls,respectively, wherein said method comprises the steps of controllingthermal crown during rolling by applying roll bending force on saidworking rolls, controlling body crown at a central portion of the platewidth by crossing the roll axes of said intermediate rolls in ahorizontal plane against a perpendicular direction to the rollingmaterial traveling direction, or shifting said intermediate rolls alongthe roll axis direction.
 24. A rolling method of a cold rolling millcomprising a pair of working rolls each, provided with a roll-contourshape having a portion thickened-toward-end which increases in diametertoward a roll end in the vicinity of the roll end on one end side of aroll barrel portion thereof, said working rolls being arranged so thatsaid thickened-toward-end portions are positioned at places on theopposite sides of the barrel portions in the roll axis direction, andsupport rolls supporting said working rolls, respectively, wherein saidmethod comprises the steps of controlling thermal crown during rollingby applying roll bending force on said working rolls, and controllingbody crow at a central portion of the plate depth by shifting saidsupport rolls along a roll axis direction.
 25. A rolling method of acold rolling mill comprising a pair of working rolls each, provided witha roll-contour shape having a portion thickened-toward-end whichincreases in diameter toward a roll end in the vicinity of the roll endon one end side of a roll barrel portion thereof, and rolling rollingmaterials, said working rolls being arranged so that saidthickened-toward-end portions are positioned at places on the oppositesides of the barrel portions in the roll axis direction, and supportrolls supporting said working rolls, respectively, wherein said methodcomprises the steps of controlling thermal crown during rolling byapplying roll bending force on said working rolls, and controlling bodycrow at a central portion of the plate depth by crossing the roll axesof said work rolls in a horizontal plane against a perpendiculardirection to the rolling material traveling direction.